
Left: the 1973 Feynman interview, by Nova, wherein he compares beliefs in witches to belief in brushing teeth. Right: the 1983 Feynman interview, second one by Christopher Sykes (Ѻ), entitled “The Fun to Imagine”, wherein Feynman is probed on his religious beliefs.

In science, Feynman on religion refers to the discussions, lectures, and or publications on the topic of God, existence of god, morality, life, meaning, death, i.e. religion in general, of American physicist Richard Feynman.

Overview
American physicist Richard Feynman (1918-1988) and his younger sister Joan Feynman (1927-) were siblings of American Lucille Feynman, a homemaker, and Belarus-born American Melville Feynman, a businessman, albeit one with a inkling to be a cultured scientist, both of whom were Ashkenazi Jews, according to census. His father, as his Richard reports, was a non-believing Jew. [1] His mother, however, seems to have had some religious conviction, as per her reaction responses tell; namely, in 1979, Omni Magazine named Feynman “The Smartest Man in the World”, following their interview with him. When his mother Lucille heard about this, her response was: “Our Richie? The world's smartest man? God help us!” (Ѻ)

In Jun 1945, Feynman’s school sweetheart turned wife, Arline Feynman (Arline Greenbaum), passed away at age 25, from tuberculosis, in their fourth year of marriage.

On 8 Oct 1946, Feynman’s father Melville Feynman died (dereacted) from a stroke.

During his father’s interment, at Bayside Cemetery, nearby Queens, Feynman, then age 29, was asked by Rabbi Cahn to say the Kaddish, i.e. a hymn of praises to God found in the Jewish prayer service, with him. Feynman refused. His sister Joan, according to interviews with his sister by biographer James Gleick, “watched in anguish as her brother’s face froze. He wanted no part in a mourner’s prayer in praise of God.” Gleick comments on this: [2]

“Feynman did not believe in God; he knew that is father had not believed in God; and the hypocrisy seemed unbearable. His disbelief had nothing of indifference in it. It was determined, coolly rational disbelief, a conviction that the myths of religion cheated knowledge. He stood there surrounded by stone and grass near the undersized sepulchral vaults, assembled on atop another, that held the bones of his grandparents. One shelf, too held the remains of his infant brother, Henry, memorialized now for twenty-two years after his life of one month. One Feynman’s face was a look of tension and determination and also, it seemed to Joan at that moment, utter isolation. Leaving his father’s coffin, he exploded in a rage. Their mother broke down and wept.”

Shortly after his father’s funeral, that Oct, Feynman wrote a curious letter, addressed to his deceased wife, one that remained sealed until after his own reaction end, in 1988, in which he states, among other things, the following: [3]

“I find it hard to understand in my mind what it means to love you after you are dead. You, dead, are so much better than anyone else alive.”

at the end of which he writes that he needs to be excused for not mailing the letter, because, as he says: “I don't know your new address.”

In 1956, Feynman, during a lunchtime talk at Caltech, stated the following: [4]

“A young man, brought up in a religious family, studies a science, and as a result he comes to doubt — and perhaps later to disbelieve in — his father's God. Now, this is not an isolated example; it happens time and time again. Although I have no statistics on this, I believe that many scientists — in fact, I actually believe that more than half of the scientists — really disbelieve in their father's God; that is, they don't believe in a God in a conventional sense. Now, since the belief in a God is a central feature of religion, this problem that I have selected points up most strongly the problem of the relation of science and religion. Why does this young man come to disbelieve? The first answer we might hear is very simple: You see, he is taught by scientists, and—as I have just pointed out—they are all atheists at heart, so the evil is spread from one to another. But if you can entertain this view, I think you know less of science than I know of religion.”

In 1963, Feynman, in his John Danz lecture “A Scientist Looks at Society”, stated the following: [5]

“Throughout the ages, men have tried to fathom the meaning of life. They realize that if some direction or some meaning could be given to the whole thing, to our actions, then great human forces would be unleased. Very many answers have been given to the question of the meaning of it all. But they have all been of different sorts. I may say that we do not know what is the meaning of life and what are the right moral values, that we have no way to choose them and so on. No discussion can be made of moral values, of the meaning of life and so on, without coming to the great source of systems of morality and descriptions of meaning, which is in the field of religion. I do believe there is a conflict between science and religion.”

Feynman then goes on to re-tell the "young man" parable.

Purpose | Meaning
The following seems to be Feynman's final states on meaning and purpose:

“I can live with doubt and uncertainty and not knowing. I think it’s much more interesting ‘not knowing’ than to have answers that might be wrong. I have approximate answers and possible beliefs and different degrees of certainty about different things, but I’m not absolutely sure of anything, and there are many things I don’t know anything about such as whether it means anything to ask ‘why we’re here?’ and what the question might mean; I might think about it a little bit, and if I can’t figure it out, I’ll move on to something else, but I don’t have to know an answer, I don’t feel frightened by not knowing things, by being lost in a mysterious universe without having any purpose, which is the way it is, as far as I can tell, possibly. It doesn’t frighten me.”
— Richard Feynman (1981), Christopher Sykes “The Pleasure of Finding Things Out” interview (Ѻ) documentary, age 63

Atheist's creed
The following seems to be Feynman's atheist’s creed, so to say:

“Believe in the fact that all things are made of atoms.”
— Richard Feynman (1964), on which sentence (Ѻ) should be passed on to the next generation of creatures, should a cataclysm occur

Quotes
The following are related quotes:

“Religion is a culture of faith; science is a culture of doubt.”
— Richard Feynman (c.1960) (Ѻ)

References
1. (a) Richard Phillips Feynman – MacHistory.
(b) Joan Feynman – Wikipedia.
2. Gleick, James. (1992). Genius: the Life and Science of Richard Feynman (pg. #). Open Road Media, 2011.
3. (a) Feynman, Richard. (1946). “Letter to Arline Feynman” (Ѻ), Oct.
(b) Gleick, James. (1992). Genius: the Life and Science of Richard Feynman (pg. #). Open Road Media, 2011.